JP3263799B2 - Surface treatment method of valve lifter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment method for coating an outer peripheral surface of a valve lifter formed of a light metal such as aluminum or an alloy thereof with a wear-resistant material.

[0002]

2. Description of the Related Art A valve lifter (tappet) used for a direct-acting type valve train in an internal combustion engine has been generally formed by molding its main body from iron or a ferrous material such as cast iron. Recently, there has been a tendency to use aluminum alloys in order to further reduce the weight of the valve train.

However, valve lifters made of aluminum alloy have lower mechanical strength and lower abrasion resistance than those made of iron-based material. Therefore, especially, this valve lifter is applied to a cylinder head made of aluminum alloy made of the same material. If incorporated, the sliding surfaces of each other will be worn out early, or galling will occur.

In order to prevent this, an outer peripheral surface of a valve lifter made of an aluminum alloy is coated with a wear-resistant material different from a base material.

[0005] At this time, the adhesion of the wear-resistant material is enhanced,
It is necessary to improve the adhesion strength to the base material, but as one means for that, after roughening the surface to be coated,
There is a method of performing a surface treatment with a wear-resistant material.

[0006] As a method for forming the above-mentioned rough surface, when the surface treatment is performed by, for example, a thermal spraying method, it is common to use a blast treatment with grit having a predetermined particle size.

[0007]

In recent years, the permissible rotational speed and the maximum output of the engine have been increasing, and the stress (bending or shear stress) acting on the outer peripheral surface of the valve lifter has also been increasing. Therefore, in particular, in a valve lifter having a structure in which the outer peripheral surface of the above-described aluminum alloy base material is coated with a wear-resistant material, a high adhesion strength of the coating layer to the base material is required.

[0008] However, in the method of performing the surface treatment by thermal spraying after performing the blasting once with grit as in the above-mentioned conventional technique, although a certain degree of adhesion strength of the coating layer can be obtained, it is not sufficient. There is a problem in durability and reliability.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and by improving the adhesion of a coating layer to a base material, the adhesion strength is improved, and a valve lifter excellent in durability and reliability is obtained. It is an object of the present invention to provide a surface treatment method for a valve lifter.

[0010]

In order to achieve the above-mentioned object, the present invention provides a method of forming a grit on at least the outer peripheral surface of a cylindrical valve lifter body having a closed upper surface.
After subjected to the primary blast treatment for the strike material is a blasting material for the primary blasting to the surface Gris
It is characterized in that a second blasting process is performed using alumina having a smaller particle size than the blast material as a blast material , and a coating layer made of a wear-resistant material is formed on the surface thereof.

Further , the present invention provides a cylindrical type having a closed upper surface.
At least on the outer peripheral surface of the valve lifter body,
First blasting process using cut wire as blast material
After the application, the surface for the first blast treatment is applied to the surface.
Brass with smaller grain size than cut wire as the last material
Secondary blasting with a metal material, the surface of which
Characterized by forming a coating layer of wearable material
You.

[0012]

After performing the primary blasting, the secondary blasting is performed by using a blasting material having a smaller particle size than the blasting material, and the roughened surface formed by the primary blasting and having a large roughness amplitude is obtained. An uneven surface with a small amplitude is formed on the surface.

Therefore, when a coating layer is formed on the outer peripheral surface of a valve lifter body made of a light metal such as aluminum or an alloy thereof by spraying or the like, an anchoring action occurs, and the adhesion of the coating layer is significantly improved.

[0014]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a valve lifter formed by applying the method of the present invention. A cylindrical valve lifter body (hereinafter abbreviated as a lifter body) having a closed upper surface (1) is formed of aluminum or an alloy thereof. Have been.

A wear-resistant shim (3) made of steel or cast iron is detachably fitted into a circular recess (2) formed on the upper surface of the lifter body (1), and the upper surface is not shown. It comes into contact with the rotating cam.

A steel or cast iron tip (5) with which the shaft end of an engine valve (not shown) abuts is provided in a small-diameter concave groove (4) formed at the center of the inner bottom surface of the lifter body (1). It is inserted.

A hard coating layer (6) made of, for example, an inexpensive iron-based wear-resistant metal material is provided on the outer peripheral surface of the lifter body (1).
Are formed through the following surface treatment steps. That is, as shown in FIG. 2, first, the entire outer peripheral surface of the lifter main body (1) is subjected to primary blasting, and as shown in an enlarged view in FIG. 7)
To form

The blast material used for the first blasting treatment is hard and has a relatively large particle size, for example, a particle size of # 12 to # 12.
Grit such as cast steel of about # 46 (JIS) is preferable, and the surface roughness (10-point average roughness Rz) by this primary blasting process
Is preferably in the range of 60 to 300 μm.

Next, the surface subjected to the primary blast treatment is subjected to a secondary blast treatment, and as shown in an enlarged view in FIG. 4, a rough surface having a large amplitude formed by the primary blast treatment ( On the surface of 7), center line average roughness Ra4μm
Hereinafter, a fine uneven surface (8) with an amplitude of 10 points average roughness Rz 30 μm or less is formed.

The blast material used for the secondary blasting process has a relatively low specific gravity and a small particle size, for example, a particle size of # 80 to ## so as not to scrape off the uneven portion formed by the primary blast. Alumina of about 240 (JIS) is suitable.

Finally, an iron-based wear-resistant material is sprayed on the surface of the uneven surface (8) formed by the secondary blasting process.
When sprayed to a required thickness by, for example, arc spraying or plasma spraying, a hard coating layer (6) is formed on the outer peripheral surface of the lifter body (1) as shown in FIG.

After the first and second blasting treatments are performed and the coating layer (6) is formed, the lifter body (1)
Since the surface area of the outer peripheral surface is significantly increased and activated, the adhesion of the coating layer (6) becomes extremely good, and the adhesion strength is greatly improved.

In addition, the direction of the unevenness of the uneven surface (8) is random, and the lifter main body (1) is formed by the anchor (anchor) effect when the concave portion and the primary blast enter into and closely adhere to the large amplitude concave portion. The adhesion and the shear strength at the boundary between the coating and the coating layer (6) are increased.

The blast material used for the primary blasting may be a cut wire (W) as shown in FIG. 5 instead of the grit. That is, the cut wire (W) has a diameter of 0.6 to 2.0 mm and a hardness of H
v500 or higher steel (tensile steel) or stainless steel (SUS30
4, 430 etc.) is preferably cut into a length substantially equal to the wire diameter. When such a cut wire (W) is used, since it does not have a sharp corner like a grit, there is no danger of cutting into the base material and remaining on the surface,
Further, there is an advantage that the life is long and the distribution of the surface roughness can be kept uniform since re-crushing and corners are not worn out at an early stage.

The present invention is not limited to a valve lifter formed of the above-mentioned aluminum or its alloy, but is applicable to forming a coating layer on the outer peripheral surface of a valve lifter made of, for example, a magnesium alloy, a titanium alloy or iron. Can. In this case, the blast material used for the primary and secondary blasts may be appropriately selected to a material suitable for those materials.

[0026]

The present invention has the following effects. (a) According to the first and second aspects of the present invention, since the adhesion of the coating layer is extremely good, the adhesion strength of the coating layer to the lifter body is greatly improved, and a valve lifter excellent in durability and reliability can be obtained. can get. In particular, the first blast process
Rough surface with relatively large amplitude is applied to the surface of the lifter body
Formed by the secondary blasting process,
Without scraping off the irregularities formed by the strike process,
It is possible to form a rough surface with fine amplitude on the rough surface
You. (b) According to the invention as set forth in claims 3 to 5, adhesion of the coating layer
Since the coating properties are extremely good, the coating layer
The adhesion strength is greatly improved, and the durability and reliability
Not only can a lubricator be obtained, but the blast material can be lifter
Bites into body, re-crushes, corners wear out early
Of the surface is uniform and the surface roughness is evenly distributed.
Can be (c) According to the seventh aspect of the present invention, the coating layer can be easily formed, and can evenly adhere to the uneven portions on the surface of the lifter main body. (d) According to the invention of claim 8 , the surface area of the outer peripheral surface of the lifter main body is increased, and the anchor (anchoring) effect is increased. Therefore, the adhesion and the shear strength of the boundary between the lifter main body and the coating layer are reduced. Increase.

[Brief description of the drawings]

FIG. 1 is a front view in central section of a valve lifter obtained by applying the present invention.

FIG. 2 is a partially cutaway front view of the valve lifter after the first blast processing.

FIG. 3 is an enlarged view of a portion A in FIG. 2;

FIG. 4 is an enlarged view of a portion B in FIG.

FIG. 5 is an enlarged perspective view of a cut wire used for a primary blasting process.

[Explanation of symbols]

 (1) Valve lifter body (2) Recess (3) Shim (4) Groove (5) Chip (6) Coating layer (7) Rough surface (8) Uneven surface (W) Cut wire

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F01L 1/14 C23C 4/02

Claims (8)

(57) [Claims] A grit is applied to at least an outer peripheral surface of a cylindrical valve lifter body having an upper surface closed.
After subjected to the primary blast treatment for the strike material is a blasting material for the primary blasting to the surface Gris
Tsu DOO be subjected to a secondary blasting a small alumina grain size and the blast material from the surface treatment method of the valve lifter, which comprises forming a coating layer of wear-resistant material on its surface. 2. A grit particle size is in the JIS # 12~ # 46, the surface treatment method of the valve lifter according to claim 1, wherein the particle size of the alumina is JIS # 80~ # 240. 3. A cut wire is provided on at least an outer peripheral surface of a cylindrical valve lifter body having a closed upper surface.
After subjected to the primary blasting and blasting material is the blasting material for the primary blasting to the surface
A second blast material with a smaller grain size than the cut wire
A surface treatment method for a valve lifter, wherein a blast treatment is performed, and a coating layer of a wear-resistant material is formed on the surface. 4. A cut wire having a diameter of 0.6 to 2.0 mm and a length substantially equal to the diameter.
4. The method of surface treating a valve lifter according to 3 . 5. A cutting wire is made of steel or stainless steel, and the hardness of Hv500 or more claims 3
Or the surface treatment method of the valve lifter according to 4 . 6. The surface treatment method for a valve lifter according to claim 1 , wherein the valve lifter main body is formed of light metal. 7. A surface treatment method of the valve lifter according to any one covering layer of claims 1 to 6, which is formed by a spraying method. 8. Surface roughness (R) by primary blasting
The surface treatment method for a valve lifter according to any one of claims 1 to 7 , wherein z) is 60 to 300 µm and surface roughness (Rz) by secondary blasting is 30 µm or less.